From e5e7c26f3953ddc05b0d7a128ec97585978d4508 Mon Sep 17 00:00:00 2001
From: Marcus Brummer <mbrlabs7@gmail.com>
Date: Thu, 29 Aug 2024 21:39:11 +0200
Subject: [PATCH] Brush stroke smoothing using cubic bezier curves

It feels so much better!
---
 lorien/BrushStroke/BrushStrokeOptimizer.gd |  4 ++--
 lorien/InfiniteCanvas/Tools/BrushTool.gd   | 13 +++++++++++--
 lorien/Misc/Utils.gd                       | 15 +++++++++++++++
 3 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/lorien/BrushStroke/BrushStrokeOptimizer.gd b/lorien/BrushStroke/BrushStrokeOptimizer.gd
index 8d79491e..3ef1f276 100644
--- a/lorien/BrushStroke/BrushStrokeOptimizer.gd
+++ b/lorien/BrushStroke/BrushStrokeOptimizer.gd
@@ -1,8 +1,8 @@
 class_name BrushStrokeOptimizer
 
 # -------------------------------------------------------------------------------------------------
-const ANGLE_THRESHOLD := 1.0
-const DISTANCE_THRESHOLD := 2.0
+const ANGLE_THRESHOLD := 0.5
+const DISTANCE_THRESHOLD := 1.0
 
 # -------------------------------------------------------------------------------------------------
 var points_removed := 0
diff --git a/lorien/InfiniteCanvas/Tools/BrushTool.gd b/lorien/InfiniteCanvas/Tools/BrushTool.gd
index 3f637d47..a15a03a6 100644
--- a/lorien/InfiniteCanvas/Tools/BrushTool.gd
+++ b/lorien/InfiniteCanvas/Tools/BrushTool.gd
@@ -39,15 +39,24 @@ func _process(delta: float) -> void:
 	if performing_stroke:
 		var pos := _cursor.global_position
 		
-		# Basic smoothing
+		# Smoothing
 		var diff := pos.distance_squared_to(_last_accepted_position)
 		if diff <= MOVEMENT_THRESHOLD || _current_pressure <= MIN_PRESSURE:
 			return
-
+		
+		var points := get_current_brush_stroke().points
+		if points.size() > 3:
+			var p3 := points[-3]
+			var p2 := points[-2]
+			var p1 := points[-1]
+			# TODO: expose the smoothing factor in the settings
+			pos = Utils.cubic_bezier(p3, p2, p1, pos, 0.75)
+		
 		var sensitivity: float = Settings.get_general_value(
 			Settings.GENERAL_PRESSURE_SENSITIVITY, Config.DEFAULT_PRESSURE_SENSITIVITY
 		)
 		
+		# Pressure
 		var point_pressure := pressure_curve.sample(_current_pressure) * sensitivity
 		if _first_point:
 			point_pressure *= 1.4
diff --git a/lorien/Misc/Utils.gd b/lorien/Misc/Utils.gd
index cae924fb..bac3e5f7 100644
--- a/lorien/Misc/Utils.gd
+++ b/lorien/Misc/Utils.gd
@@ -85,3 +85,18 @@ func translate_action(action_name: String) -> String:
 # Does an _exact_ match for the given key stroke.
 func event_pressed_bug_workaround(action_name: String, event: InputEvent) -> bool:
 	return InputMap.action_has_event(action_name, event) && event.is_pressed() && !event.is_echo()
+
+# -------------------------------------------------------------------------------------------------
+func cubic_bezier(p0: Vector2, p1: Vector2, p2: Vector2, p3: Vector2, t: float) -> Vector2:
+	var q0 := p0.lerp(p1, t)
+	var q1 := p1.lerp(p2, t)
+	var q2 := p2.lerp(p3, t)
+	var r0 := q0.lerp(q1, t)
+	var r1 := q1.lerp(q2, t)
+	return r0.lerp(r1, t)
+
+# -------------------------------------------------------------------------------------------------
+func quadratic_bezier(p0: Vector2, p1: Vector2, p2: Vector2, t: float) -> Vector2:
+	var q0 := p0.lerp(p1, t)
+	var q1 := p1.lerp(p2, t)
+	return q0.lerp(q1, t)